Detergent compositions containing alpha-sulfofatty acid esters and methods of making and using the same

ABSTRACT

The present invention includes a composition comprising an enriched mixture of α-sulfofatty acid esters. Increasing the concentration of specific chain length α-sulfofatty acid esters, relative to the proportions of the other chain lengths, allows the detergent compositions to exhibit an improved cleaning performance while simultaneously cleaning a wide variety of materials.

BACKGROUND OF THE INVENTION

The present invention generally relates to α-sulfofatty acid estercompositions and methods for making and using such compositions. Moreparticularly, the present invention relates to α-sulfofatty acid estercompositions that are enriched for particular α-sulfofatty acid esters,and methods for making and using such compositions.

Detergents have been used for many years to clean clothing and othermaterials. Detergent compositions are generally formulated to containcomponents such as surfactants, builders, electrolytes and otheradditives dispersed or dissolved in an aqueous medium. Surfactants areincluded in detergents to enhance their cleaning performance. Typicalsurfactants include anionics, nonionics, zwitterionics, ampholytics,cationics and those described in Surface Active Agents, Volumes I and IIby Schwartz, Perry and Berch (New York, Interscience Publishers),Nonionic Surfactants ed. by M. J. Schick (New York, M. Dekker, 1967),and in McCutcheon's Emulsifiers & Detergents (1989 Annual, M. C.Publishing Co.), the disclosures of which are incorporated herein byreference.

Recently, interest in α-sulfofatty acid esters (also referred tohereinafter as “sulfofatty acids”) has increased due to the superiorcleaning properties of these surfactants in hard water. While othersurfactants have similar detergency in soft water, as water hardnessincreases α-sulfofatty acid esters exhibit increased cleaningperformance as compared with other anionic surfactants. Thus,α-sulfofatty acid esters are an effective anionic surfactant that can beused in a wide variety of washing conditions.

α-Sulfofatty acid esters are typically manufactured as salts (i.e., amixture of salt forms, typically mono- and di-salts). Di-salts resultfrom hydrolysis of α-sulfofatty acid ester during manufacture, storageand in detergent compositions. In particular, mono-salts of α-sulfofattyacid ester hydrolyze in the presence of moisture and alkali-containingdetergent components to form di-salts. For example, in formulationscontaining methyl ester sulfonate (“MES”) that is well mixed with highpH components under aqueous conditions, the MES will hydrolyze nearlycompletely to the di-salt form. Such high pH components can includebuilders, such as silicates or carbonates, and bases. This chemicalinstability discourages the use of such anionic surfactants in manyapplications.

α-Sulfofatty acid esters are typically made from natural fats or oils.These fats and oils are usually free fatty acids or glycerol esters(i.e., mono-, di- or triglycerides). Free fatty acids are formed fromglycerol esters by hydrolysis. The resulting fatty acids typicallycontain an even number of carbon atoms. These fatty acids are thenesterified to form fatty acid esters. The esters are then sulfonated toform α-sulfofatty acid esters.

The surface active agent properties of α-sulfofatty acid esters arerelated to the chain lengths of the fatty acid portion of the molecules.For example, shorter chain length molecules (e.g., C₈-C₁₂ α-sulfofattyacid esters) are typically more water-soluble, but exhibit lessersurface active agent properties. Longer chain length (e.g., C₁₄-C₁₆)α-sulfofatty acid esters exhibit greater surface active agentproperties, but are less water-soluble. Because α-sulfofatty acid estersare usually manufactured from natural sources, they are a mixture ofdifferent chain lengths. The properties of such mixtures are determinedby the chain length distribution of the source of the fatty acids. Thus,α-sulfofatty acid esters from palm kernel (stearin) oil have differentsurfactant properties than α-sulfofatty acid esters from tallow. Toovercome the limitations of single sources, blends of α-sulfofatty acidesters from multiple sources are prepared. Such blends are also limited,however, by the chain length distributions of each fatty acid source.For example, combining α-sulfofatty acid esters from palm kernel(stearin) oil (C₆-C₂₀ fatty acids) with α-sulfofatty acid esters fromtallow (C₁₄-C₁₈ fatty acids) creates a mixture that has the averagecharacteristics of the α-sulfofatty acid esters contained therein.

It has not been previously appreciated that the properties ofα-sulfofatty acid ester mixtures can be improved by enriching suchmixtures with particular chain length α-sulfofatty acid esters. Suchenrichment allows certain beneficial properties (associated withparticular chain length α-sulfofatty acid ester) to be enhanced withoutdiluting such mixtures with other α-sulfofatty acid ester chain lengths.

SUMMARY OF THE INVENTION

The present invention provides compositions and processes for enrichingmixtures of α-sulfofatty acid esters for particular chain lengths. Byincreasing the proportion of particular chain length α-sulfofatty acidesters, compositions are prepared that exhibit improved cleaningperformance as well as improved aqueous solubility and reduced phaseseparation of the α-sulfofatty acid esters from other aqueouscomponents.

The present invention includes compositions that are enriched forparticular chain length α-sulfofatty acid ester(s). In one embodiment, amixture of α-sulfofatty acid esters is enriched for a particular chainlength α-sulfofatty acid ester. In another embodiment, a mixture ofα-sulfofatty acid esters is enriched for a range of α-sulfofatty acidester chain lengths. Such mixtures are enriched for a narrow range ofsuch sulfofatty acid chain lengths or for multiple discrete chainlengths. Detergent components can also be added to the enriched mixtureof α-sulfofatty acid esters. Suitable detergent components includebuilders, other anionic surfactants, nonionic surfactants, cationicsurfactants, zwitterionic surfactants, polymer dispersants, oxidizingagents, biocidal agents, foam regulators, binders, anticaking agents,activators, catalysts, thickeners, stabilizers, UV protectors,fragrances, soil suspending agents, fillers, brighteners, enzymes,salts, inert ingredients, and the like.

Processes for enriching mixtures of α-sulfofatty acid esters are alsoprovided. In one embodiment, a mixture of α-sulfofatty acid esters isenriched for one or more α-sulfofatty acid esters of particular chainlengths. For example, α-sulfofatty acid esters prepared from cohune oil,palm kernel oil or coconut oil are enriched for C₁₆ α-sulfofatty acidester. In another embodiment, a mixture of α-sulfofatty acid esters isenriched for a narrow range of α-sulfofatty acid ester chain lengths.The α-sulfofatty acid ester mixture is enriched, for example, bysupplementing the fatty acid feedstock with particular chain lengthfatty acid(s), by enriching for particular chain length fatty acid alkylester(s) prior to sulfonation, and/or by the addition of particularchain length α-sulfofatty acid esters to a mixture of such α-sulfofattyacids.

DETAILED DESCRIPTION OF THE INVENTION

The following description provides specific details, such as materialsand dimensions, to provide a thorough understanding of the presentinvention. The skilled artisan, however, will appreciate that thepresent invention may be practiced without employing these specificdetails. Indeed, the present invention can be practiced in conjunctionwith processing, manufacturing or fabricating techniques conventionallyused in the detergent industry. Moreover, the processes below describeonly steps, rather than a complete process flow, for manufacturing theinventive compositions, and detergents containing the inventedcompositions.

A preferred embodiment is directed to compositions comprising enrichedmixtures of α-sulfofatty acid esters. The mixture of α-sulfofatty acidesters include linear esters of C₆ to C₂₀ α-sulfofatty acid esters. Theα-sulfofatty acid esters are typically of the following formula (I):

where R₁ is an unsubstituted or substituted alkyl group, R₂ is anunsubstituted or substituted alkyl group, and R₃ is hydrogen, a halogen,a metal, a monovalent or divalent cation, or an unsubstituted orsubstituted ammonium cation, such as monoethanolamine, diethanolamine,or triethanolamine. R₁ can be a C₄ to C₂₄ alkyl group including a C₁₀,C₁₂, C₁₄, and C₆ alkyl group. R₂ can be a C₁ to C₈ alkyl group,including a methyl group. R₃ can be a metal, including a cation thatforms a water soluble salt with the α-sulfofatty acid ester, such assodium, potassium or lithium.

More typically, the α-sulfofatty acid ester is of the following formula(II):

wherein R₁ is an alkyl group, R₂ is an alkyl group, and M is amonovalent metal. Typically, R₁ is an alkyl group containing 4 to 24carbon atoms, such as a C₁₀, C₁₂, C₁₄, and C₆ alkyl group. R₂ istypically a C₁ to C₄ alkyl group, and is more typically a methyl group.M is typically an alkali metal, such as sodium.

The mixture of α-sulfofatty acid esters is prepared according to thedesired properties of the final composition. Each α-sulfofatty acidester is typically at least 50 weight percent mono-salt, preferably atleast about 70 weight percent mono-salt. Methods of manufacturingα-sulfofatty acid esters are known to the skilled artisan. (See, e.g.,U.S. Pat. Nos. 5,587,500; 5,329,030; 5,382,677; 5,384,422; 4,671,900;4,816,188; and The Journal of American Oil Chemists Society 52:323-29(1975); the disclosures of which are incorporated herein by reference.)The mixture of α-sulfofatty acid esters can be manufactured according toany of these methods. α-Sulfofatty acid esters can be prepared from avariety of sources, including beef tallow, palm kernel oil, palm oil,peanut oil, coconut oil, soybean oil, canola oil, caster oil, cohuneoil, coco butter, palm oil, white grease, cottonseed oil, corn oil,linseed oil, rape seed oil, yellow grease, tall oil, butter, lard, andmixtures thereof.

Other sources of fatty acids to make α-sulfofatty acid esters includecaprylic (C₈), capric (C₁₀), lauric (C₁₂), myristic (C₁₄), myristoleic(C₁₄), palmitic (C₁₆), palmitoleic (C₁₆), stearic (C₁₈), oleic (C₈),linoleic (C₁₈), linolenic (C₁₈), ricinoleic (C,₈), arachidic (C₂₀),gadolic (C₂₀), behenic (C₂₂) and erucic (C₂₂) fatty acids. α-Sulfofattyacid esters made from these sources are also within the scope of thepresent invention.

In one embodiment, the mixture of α-sulfofatty acid esters is a “broadcut.” As used herein, the term “broad cut” refers to a mixturecomprising at least 1% of C₁₀, C₁₂, C₁₄, C₁₆ and C₁₈ α-sulfofatty acidesters. Suitable sources of fatty acids that contain such a broad cutinclude palm kernel oil, coconut oil and cohune oil. In anotherembodiment, the mixture of α-sulfofatty acid esters is a “narrow cut,”such as a mixture of C₁₂ and C₁₄ α-sulfofatty acid esters, a mixture ofC₁₆ and C₁₈ α-sulfofatty acid esters, and the like. In anotherembodiment, different chain length α-sulfofatty acid esters are combinedto form a mixture. For example, C₁₆ and C₁₈ sulfofatty acids (e.g., fromtallow and/or palm stearin) generally provide better surface activeagent properties, but can be less soluble. C₈-C₁₄ sulfofatty acids(e.g., from palm kernel and/or coconut) are more soluble in water, buthave lesser surface active agent properties. Thus, suitable mixtures ofα-sulfofatty acid esters include, for example, about 1 to about 100weight percent of C₈, C₁₀, C₁₂, C₁₄, C₁₆ and C₁₈ α-sulfofatty acidesters. Other mixtures of α-sulfofatty acid esters are also within thescope of the present invention, as will be appreciated by the skilledartisan.

The mixture of α-sulfofatty acid esters is enriched for one or morechain length α-sulfofatty acid esters. As used herein, the term“enriched” means that the proportion of one or more chain lengthα-sulfofatty acid esters is increased relative to the proportionnormally found in the α-sulfofatty acid ester mixture. For example,α-sulfofatty acid esters prepared from palm kernel oil and coconut oiltypically comprise about 8.7 and 9 percent C₁₆ α-sulfofatty acid esters.Such mixtures can be enriched by adding additional C₁₆ α-sulfofatty acidesters. The resulting enriched mixture exhibits superior cleaningperformance, good solubility and reduced phase separation. In anotherembodiment, the mixture of α-sulfofatty acid esters is enriched with anarrow range of α-sulfofatty acid esters. For example, α-sulfofatty acidesters prepared from palm kernel oil or cohune oil are typically amixture of C₆-C₁₈ chain lengths. α-Sulfofatty acid esters derived frombeef tallow are predominately C₁₆-C₁₈ α-sulfofatty acids. A narrow rangefraction of α-sulfofatty acid esters from tallow can comprise about 96percent C₁₆, about 3% C₁₄ and about 1% C₁₈ α-sulfofatty acid esters.Thus, α-sulfofatty acid esters prepared from palm kernel oil or cohuneoil are enriched with the narrow range (e.g., C₁₆) fraction from tallowto form an enriched mixture of α-sulfofatty acid esters. In anotherembodiment, the narrow range comprises less than about 10%, moretypically less than about 5%, of α-sulfofatty acid esters other than thepredominant (e.g., C₁₆) α-sulfofatty acid ester. In still anotherembodiment, a mixture of shorter chain length (α-sulfofatty acid esters(e.g., C₁₀, C₁₂ and C₁₄) is enriched with longer chain lengthα-sulfofatty acid(s) (e.g., C₁₆ and/or C₈) to form an enriched mixture.

The mixture of α-sulfofatty acid esters can be enriched by addingparticular chain length α-sulfofatty acid ester(s) to that mixture. Amixture of α-sulfofatty acid esters can also be enriched by selectivelyremoving non-preferred chain length α-sulfofatty acid esters from thatmixture. The amount of enrichment can be chosen according to the desiredproperties of the final enriched mixture. For example, suitableproportions of enriched chain lengths to non-enriched chain lengths willinclude, but are not limited to, about 25 to about 50 weight percentenriched chain length to about 75 to about 50 weight percentnon-enriched chain lengths. In another embodiment, the ratio of enrichedto non-enriched chain lengths can range from greater than about 0.5:1,typically about 1:1 or about 2:1, and up to about 5:1 or about 6:1.

In some embodiments, the enriched mixture of α-sulfofatty acid esters ispart of a detergent composition. Such detergent compositions preferablycontain an effective amount of the α-sulfofattty acid ester mixture(i.e., an amount which exhibits the desired cleaning and surfactantproperties). Typically, the detergent composition contains at leastabout 5 weight percent of the enriched α-sulfofatty acid ester mixture.More typically, the detergent composition contains at least about 15weight percent of the enriched α-sulfofatty acid ester mixture. Inanother embodiment, the detergent composition contains at least about 30weight percent, and/or at least about 35 weight percent, of the enrichedα-sulfofatty acid ester mixture.

Suitable detergent components that can be combined with the enrichedα-sulfofatty acid ester mixture include builders, other anionicsurfactants, nonionic surfactants, cationic surfactants, zwitterionicsurfactants, polymer dispersants, oxidizing agents, biocidal agents,foam regulators, binders, anticaking agents, activators, catalysts,thickeners, stabilizers, UV protectors, fragrances, soil suspendingagents, fillers, brighteners, enzymes, salts, inert ingredients, and thelike.

Suitable non-ionic surfactants include those containing an organichydrophobic group and a hydrophilic group that is a reaction product ofa solubilizing group (such as a carboxylate, hydroxyl, amido or aminogroup) with an alkylating agent, such as ethylene oxide, propyleneoxide, or a polyhydration product thereof (such as polyethylene glycol).Such nonionic surfactants include, for example, polyoxyalkylene alkylethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene sorbitanfatty acid esters, polyoxyalkylene sorbitol fatty acid esters,polyalkylene glycol fatty acid esters, alkyl polyalkylene glycol fattyacid esters, polyoxyethylene polyoxypropylene alkyl ethers,polyoxyalkylene castor oils, polyoxyalkylene alkylamines, glycerol fattyacid esters, alkylglucosamides, alkylglucosides, alkylamine oxides, andalkanolamides. Other suitable surfactants include those disclosed inU.S. Pat Nos. 5,133,892 and 6,034,045, the disclosures of which areincorporated herein by reference. In one embodiment, the composition issubstantially free of nonylphenol nonionic surfactants. In this context,the term “substantially free” means less than about 1 weight percentnonylphenol nonionic surfactant.

Suitable builders include silicated salts. The term “silicated salt”means a non-phosphate salt, such as a carbonate, sulfate, alkali metalcarbonate, alkali metal sulfate, ammonium carbonate, bicarbonate,sesquicarbonate, or mixtures thereof, that has been treated with asilicate salt. Silicated salts and methods for preparing such salts aredisclosed in U.S. Pat. No. 4,973,419, the disclosure of which isincorporated herein by reference.

Suitable silicate builders include non-phosphate silicate salts, such aspolysilicates and alkali metal silicates. One preferred alkali metalsilicate is a sodium silicate, such as a hydrous sodium silicate havingan SiO₂ to Na2O ratio ranging from about 2.0 to about 2.4. Suitablealkali metal silicates further include those sold by PQ Corporationunder the trade names BRITESIL® H20, BRITESIL® H24 and BRITESIL® C-24.Other suitable silicate builders include wholly or partially crystallitelayer-form silicates of the formula Na₂Si_(x).O_(2x+1)yH₂0, where xranges from about 1.9 to about 4 and y ranges from 0 to about 20. Suchsilicates are described, for example, in U.S. Pat. No. 5,900,399, thedisclosure of which is incorporated herein by reference.

Other suitable silicate builders include phyllosilicates or disilicates,such as those having the formula Na₂O.2SiO₂ or Na₂Si₂O₅.yH₂O, where y isan integer. Preferred disilicates include β-sodium disilicates, such asthose described in International Patent Application WO-A-91-08171, thedisclosure of which is incorporated herein by reference. Disilicatessold under the trade names SKS® 6 and SKS® 7 by Hoescht AG and ClariantCorporation can also be used.

Other suitable builders include phosphate and aluminosilicate builders.The term “phosphate builders” means both inorganic and organicphosphate-containing builders such as alkali metal phosphates,orthophosphates, polyphosphates, tripolyphosphates, pyrophosphates, andpolymeric phosphates. Aluminosilicate builders include those known inthe art, such as those of the formulae (III) and (IV):

 Na_(z)[(AlO₂)_(z)(SiO₂)_(y)].xH₂0  (III)

where z and y are integers greater than 5, x is an integer ranging from15 to 264, and the molar ratio of z to y ranges from about 1.0 to about0.5; and

M_(z)(zAlO₂.ySiO₂)  (IV)

where M is sodium, potassium, ammonium, or substituted ammonium, zranges from about 0.5 to about 2, and y is 1. Examples of suchaluminosilicate builders include zeolite NaA, zeolite NaX, zeolite P,zeolite Y, hydrated zeolite 4A, zeolite MAP or mixtures thereof.

Suitable polymer dispersants include polymers and co-polymers of acrylicacid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, andwater-soluble salts thereof, such as alkali metal, ammonium, orsubstituted ammonium salts. Suitable polymer dispersants further includethose sold under the trade names ACUSOL® 445 (polyacrylic acid), ACUSOL®445N (the sodium salt of polyacrylic acid), ACUSOL® 460N (a maleicacid/olefin copolymer sodium salt), and ACUSOL® 820 (acrylic copolymer),all sold by Rohm and Haas.

Other anionic surfactants include alkylbenzenesulfonates, alkyl oralkenyl ether sulfates, alkyl or alkenyl sulfates, olefin sulfonates,alkyl or alkenyl ether carboxylates, amino acid-type surfactants, andN-acyl amino acid-type surfactants. In another embodiment, thecomposition is substantially free of other anionic surfactants.

Suitable oxidizing agents include chlorine and non-chlorine-containingoxidizing agents. Suitable non-chlorine oxidizing agents include oxygenbleaches, such as perborates, percarbonates, persulfates, dipersulfates,sodium carbonate peroxyhydrate, sodium pyrophosphate peroxyhydrate, ureaperoxyhydrate, and sodium peroxide. Other suitable non-chlorineoxidizing agents include bleach activators, such as tetraacetyl ethylenediamine (TAED), sodium benzoyl oxybenzene sulfonate, choline sulfophenylcarbonate, and those described in U.S. Pat. Nos. 4,915,854 and4,412,934, the disclosures of which are incorporated herein byreference. Other suitable non-chlorine oxidizing agents include acatalyst such as manganese or other transition metals in combinationwith such oxygen bleaches.

Other suitable oxidizing agents include percarboxylic acid bleachingagents and salts thereof, such as magnesium monoperoxyphthalatehexahydrate and the magnesium salts of meta-chloro perbenzoic acid,4-nonylamino-4-oxoperoxybutyric acid and diperoxydodecanedioic acid.Other oxidizing agents include those described in U.S. Pat. Nos.4,483,781, 4,634,551, and 4,412,934, as well as European PatentApplication No. 0,133,354, the disclosures of which are incorporatedherein by reference.

Suitable oxidizing agents include non-oxygen-containing agents, such asphotoactivated bleaching agents. Suitable photoactivated bleachingagents include sulfonated zinc and metal phthalocyanines, such asaluminum and zinc phthalocyanines. Other suitable photoactivatedbleaching agents are described in U.S. Pat. No. 4,033,718, thedisclosure of which is incorporated herein by reference.

Chlorine-containing agents include organic and/or inorganic compoundscapable of having their chlorine liberated in the form of activechlorine on dissolution in water. Typical examples of suchchlorine-containing agents include hypochlorites such as alkali metal(calcium and lithium) hypochlorites; chlorinated trisodium phosphate;chlorinated sulfonamides; halogenated hydantoins, such as1,3-dichloro-5,5-dimethylhydantoin; polychlorocyanurates (usuallycontaining alkali metals such as sodium or potassium salts);chlorine-substituted isocyanuric acid; alkali-metal salts of isocyanuricacid, such as potassium or sodium dihydrate; and other anhydrouschlorine-containing agents known in the detergent industry.

Suitable biocidal agents include TAED, TAED combined with a persalt,triclosan (5-chloro-2 (2,4-dichloro-phenoxy) phenol)), and quaternaryammonium compounds such as alkyl dimethyl ammonium chlorides, alkyltrimethyl ammonium chlorides, dialkyl dimethyl ammonium chlorides,benzalkonium chloride, parachlorometaxylene and alkyl dimethyl benzylammonium chloride. Other biocidal agents include those sold under thetrade names BARDAC® and BARQUAT® by the Lonza Group and those sold underthe trade name BTC by the Stepan Company.

Suitable optical brighteners include stilbenes such as TINOPAL® AMS,distyrylbiphenyl derivatives such as TINOPAL® CBS-X,stilbene/naphthotriazole blends such as TINOPAL® RA-16, all sold by CibaGeigy, oxazole derivatives and coumarin brighteners.

Suitable enzymes include any of those known in the art, such asamylolytic, proteolytic or lipolytic type, and those listed in U.S. Pat.No. 5,324,649, the disclosure of which is incorporated herein byreference. One preferred protease, sold under the trademark SAVINASE® byNOVO Industries A/S, is a subtillase from Bacillus lentus. Othersuitable enzymes include amylases, lipases, and cellulases, such asALCALASE® (bacterial protease), EVERLASE® (protein-engineered variant ofSAVINASE®), ESPERASE® (bacterial protease), LIPOLASE® (fungal lipase),LIPOLASE ULTRA (Protein-engineered variant of LIPOLASE), LIPOPRIME™(protein-engineered variant of LIPOLASE), TERMAMYL® (bacterial amylase),BAN (Bacterial Amylase Novo), CELLUZYME® (fungal enzyme), and CAREZYME®(monocomponent cellulase), sold by Novo Industries A/S.

Compositions according to the present invention can be prepared by anysuitable process or combination of processes that yield the desiredcomposition, according to the present invention. The enriched mixture ofα-sulfofatty acid esters is typically prepared by one of a variety ofmethods. In one embodiment, the enriched mixture of α-sulfofatty acidesters is prepared by combining particular chain length fatty acid(s)with a mixture of fatty acids of differing chain lengths. The enrichedfatty acid mixture is then esterified and sulfonated to form theenriched mixture of α-sulfofatty acid esters. In another embodiment, theenriched mixture is prepared by combining particular chain length fattyacid ester(s) with a mixture of fatty acid esters of differing chainlengths. The enriched mixture of fatty acid esters is then sulfonated toform the enriched mixture of α-sulfofatty acid esters. In yet anotherembodiment, the enriched mixture of α-sulfofatty acid esters is preparedby combining particular chain length α-sulfofatty acid ester(s) with amixture of α-sulfofatty acid esters of differing chain lengths.

In a preferred embodiment, the enriched mixture of α-sulfofatty acidesters are prepared by combining C₁₆-enriched fatty acids, C₁₆-enrichedfatty acid alkyl esters, or C ₁₆-enriched α-sulfofatty acid esters witha mixture of fatty acids, fatty acid alkyl esters or α-sulfofatty acidesters, respectively. These mixtures are esterified and sulfonated, asnecessary, to form an enriched mixture of α-sulfofatty acid esters. Theproportions of carbon chain lengths in the mixture are selectedaccording to the desired surfactant properties of the final composition.

One method of preparing an enriched mixture of α-sulfofatty acid estersis to provide a natural fat or oil that includes the preferred chainlength fatty acids, and then fractionating the fatty acids to enrich forthose preferred chain lengths. Typically, such a natural fat or oil hasa significant concentration (at least about 25 percent and preferablyabout 35 percent) of the preferred chain length fatty acids. Forexample, a suitable fatty acid source, such as palm stearine oil ortallow, is provided and fed to a separation apparatus, such as afractionation tower or liquid-liquid extraction. (See, e.g., Perry'sChemical Engineers' Handbook (6^(th) Ed.), chapter 15 (1984), thedisclosure of which is incorporated herein by reference). TheC₁₆-enriched stream exiting the separation apparatus is then combinedwith a mixture of fatty acids. The enriched mixture of fatty acids isthen esterified to make an enriched mixture of fatty acid alkyl esters,which is then sulfonated to form the enriched mixture of α-sulfofattyacid esters. The other stream(s) exiting the separation apparatus can beused in any desired manner. For example, when palm stearine oil isfractionated, the stream containing mostly C₁₆ fatty acids is used tomake the α-sulfofatty acid esters while the stream containing mostly C₁₈fatty acids is used in the process of making an alkanolamide or apolyalkoxylated alkanolamide.

Another method is to prepare fatty acid alkyl esters comprising thepreferred fatty acid alkyl esters, such as fatty acid methyl esters, andthen fractionating the fatty acid alkyl esters to enrich for preferredchain length fatty acid alkyl esters. Preferably, such fatty acid alkylesters have a significant concentration (at least about 25 percent andpreferably about 35 percent) of the desired fatty acid alkyl esters. Forexample, a suitable fatty acid alkyl ester source, such as esterifiedtallow, is provided and fed to a separation apparatus, such as afractionation tower or liquid-liquid extraction. (See, e.g., Perry'sChemical Engineers' Handbook (6^(th) Ed.), chapter 15 (1984), thedisclosure of which is incorporated herein by reference.) TheC₁₆-enriched stream exiting the separation apparatus is then used tomake C₁₆-enriched α-sulfofatty acid esters. The other stream(s) exitingthe separation apparatus can be used in any desired manner, such as tomake alkanolamides or polyalkoxylated alkanolamides.

The enriched α-sulfofatty acid ester mixture can also be prepared bycombining a mixture of α-sulfofatty acid esters with the desired chainlength α-sulfofatty acid ester(s) to enrich the mixture. For example, abroad cut mixture of α-sulfofatty acid esters from cohune oil, palmkernel oil or coconut oil can be mixed with a narrow range of C₁₆ (e.g.,C₁₄-C₁₆-C₁₈) α-sulfofatty acid esters.

Any suitable mixing apparatus can be used to combine the fatty acids,fatty acid alkyl esters or α-sulfofatty acid esters. (See, e.g., Perry'sChemical Engineers' Handbook (6^(th) Ed.), chapters 19 and 21 (1984),the disclosure of which is incorporated herein by reference.) In someembodiments, the amounts of different chain lengths can be combined inany suitable ratios. For example, when a first source of fatty acids ispalm kernel oil (PKO) and a second source of fatty acids is C₁₆-fattyacids from palm stearine oil (PSO), these two sources are mixed inamounts of about 40-60 weight percent PKO with about 60-40 weightpercent C₁₆-enriched PSO, and preferably about 50-55 weight percent PKOwith about 50-45 weight percent C₁₆-enriched PSO. The fatty acids arethen esterified to form fatty acid alkyl esters, which are thensulfonated.

In another example, when a first source of fatty acid alkyl esters isesterified palm kernel oil (ePKO) and a second source of fatty acidalkyl esters is esterified, C₁₆-enriched palm stearine oil (ePSO), thesetwo sources are mixed in amounts of about 40-60 weight percent ePKO withabout 60-40 weight percent C₁₆-enriched ePSO, and preferably about 50-55weight percent ePKO with about 50-45 weight percent C₁₆-enriched ePSO.The enriched mixture of fatty acid alkyl esters is then sulfonated toform the enriched mixture of α-sulfofatty acid esters.

The sulfonation process can be performed according to any sulfonationprocess as known in the art, such as the processes described in U.S.Pat. Nos. 5,587,500; 5,329,030; 5,382,677; 5,384,422; 4,671,900;4,816,188; and The Journal of American Oil Chemists Society 52:323-29(1975), the disclosures of which are incorporated herein by reference.Other sulfonation processes known in the art include those processesusing both hydrogen peroxide and a halogen bleach in a two stepbleaching operation; processes that use ultra purified fatty acid alkylester feedstocks along with a single step hydrogen peroxide neutralbleaching process; and re-esterification processes using only hydrogenperoxide acidic bleaching with typical quality fatty acid alkyl esterfeedstocks.

The α-sulfofatty acid ester (e.g., a methyl ester sulfonate) istypically prepared by feeding the fatty acid alkyl ester feedstock andSO₃ gas to a suitable reactor, such as a falling film reactor. Anysource of SO₃ gas can be used. For example, to generate SO₃ gas, dry airis compressed, cooled, dried and then mixed with liquid sulfur, suppliedfrom a suitable reservoir, to make sulfur dioxide. The sulfur can beuniformly combusted, for example, by using a sulfur burner to controlthe molar ratio of air to sulfur. The sulfur dioxide is cooled, such asin a double-pipe cooler, prior to being delivered to a catalyticconverter where the sulfur dioxide gas is filtered and converted to thesulfur trioxide gas.

In the sulfonation reaction, or sulfonator, the molar ratio of themethyl ester feed to the SO₃ gas is optimized for sulfonation of thefatty acid alkyl ester feedstock. The step of sulfonation is typicallythe rapid reaction of the fatty acid alkyl ester with two molecules ofSO₃ to form an adduct. The second step of the sulfonation reaction,which is usually slower and requires longer time and elevatedtemperatures, is rearrangement of the adduct to form a fatty acid alkylester sulfonic acid, releasing the second molecule of SO₃, which thenreacts with another fatty acid alkyl ester molecule. The sulfur dioxidegas that is generated in the two-step process can then be removed andcan be recycled.

The fatty acid alkyl ester sulfonic acid can optionally be bleached.Because the elevated temperatures in the sulfonation process darken theacid, a bleaching step may be required to lighten the acid to acceptablelevels. An advantageous fatty acid alkyl ester sulfonic acid feedstockused in the manufacturing process is a natural oil derivative that haslow acid values, a narrow molecular weight distribution, contains littleor no paraffinic compounds, and has been hydrogenated to reduce theiodine content, thereby reducing the presence of double bonds that causethe dark color when sulfonated. The bleaching process can be carried outin two stages. First, the fatty acid alkyl ester sulfonic acid isreacted with less than about 5 weight percent alkanol, such as methanol,to produce the desired mono-salt and to inhibit formation of the di-saltto less than about 30%. Second, hydrogen peroxide is reacted with thefatty acid alkyl ester sulfonic acid to reduce the color. The order ofthe two bleaching steps can be changed, as desired. The fatty acid alkylester sulfonic acid is typically degassed in an inert gas blanketedflash feed tank to remove oxygen and low molecular compounds.

The fatty acid alkyl ester sulfonic acid is then neutralized to formα-sulfofatty acid ester. The fatty acid alkyl ester sulfonic acid isneutralized with any suitable base that will yield the desired salt.Typically, sodium hydroxide (NaOH) is reacted with fatty acid alkylester sulfonic acid to produce sodium α-sulfofatty acid ester.

Finally, the α-sulfofatty acid ester is dried. The product leaving theneutralizer typically contains about 65-70% solids and 10-15% methanol.The α-sulfofatty acid ester is heated to an elevated temperature and fedto a dryer, preferably a steam-heated vacuum flash dryer, to strip themethanol and water (and other volatile components). The resultingproduct contains about 2-4% water. This product can optionally becooled.

In another embodiment, the α-sulfofatty acid ester is optionallypartially or fully coated to protect the α-sulfofatty acid ester frommoisture and/or minor amount of additional di-salt formation. Such acoating can prevent the contact of bases, moisture, and other di-saltcausing substances with the sulfofatty acid. Such a coating can bewater-resistant. In such an embodiment, the coating typically has amelting point within normal washing temperatures. The coating can alsobe water-soluble.

Suitable coatings include, for example, polyvinyl alcohol, partially orfully hydrolyzed polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl-methylmethacrylate copolymer, maleic acid/acrylicacid copolymer, ethylene/maleic anhydride copolymer, polyethyleneglycol, acrylic acid polymer, carboxymethyl cellulose, cellulose ether,paraffin waxes, fatty acids, methyl ester sulfonate, soaps, waxes,water-soluble polymers, water-swellable polymers, or copolymers, saltsor mixtures of any of these.

The coating can be applied to the α-sulfofatty acid ester according totechniques conventionally used in the detergent industry. Othertechniques for applying coatings, such as those used in thepharmaceutical industry, are also within the scope of the presentinvention, as will be appreciated by the skilled artisan. Examples ofsuitable techniques for applying a coating include dip coating, spincoating, spray coating, spray drying (including spray drying usingcounter-current or co-current techniques), agglomeration and fluid beddrying. Suitable fluid bed dryers include, for example, static,vibrating, high-shear granulating, vacuum fluid bed, tablet pan coating,rotor processing and high speed fluid bed dryers. Following coating atleast a portion of the α-sulfofatty acid ester, the coating can bedried, as necessary, to remove excess moisture or other liquid.

In another embodiment, the enriched mixture of α-sulfofatty acid estersis combined with other detergent components in any suitable mixingapparatus. Suitable apparatuses include dry blenders, agglomerators,spray drying equipment, fluid bed mixers, or any solid-solid,liquid-solid, or liquid-liquid mixing apparatus known in the art. (See,e.g., Perry's Chemical Engineers' Handbook (6^(th) Ed.), chapter 19(1984).) Water and/or solvents can be added to aid in this mixingprocess. Further, on exiting the mixing apparatus, the composition isoptionally dried and combined with other detergent components as knownin the art.

Other embodiments of the present invention are exemplified in thefollowing examples, which illustrate embodiments of the presentinvention, although the invention is not intended to be limited by or tothese examples.

EXAMPLE 1

A C₁₆-enriched methyl ester sulfonate was prepared according to thefollowing process. Palm kernel oil (“PKO”) and palm stearine oil (“PSO”)were separately esterified with an alkanol (e.g., methanol). Theesterified palm stearin oil was then fractionated in a tower. The C₁₆fraction of the palm stearin oil (predominately C₁₆'s with small amountsof C₁₄ and C₁₈ chain lengths) was then mixed with the esterified palmkernel oil in a ratio of about 1:1. The mixture was then sulfonated in afalling film reactor. The resulting fatty acid alkyl ester sulfonic acidwas reacted with NaOH to obtain an enriched sodium α-sulfofatty acidester.

EXAMPLE 2

A detergent composition (i.e., one with C₁₆-enriched methyl estersulfonate) is made according to the following process. First, palmkernel oil is esterified with an alkanol (e.g., methanol) to form afirst fatty acid alkyl ester. Tallow is esterified with an alkanol(e.g., methanol) to form a second fatty acid alkyl ester. The secondtallow fatty acid alkyl ester is then fractionated in a tower. TheC₁₆-enriched fatty acid alkyl ester fraction is combined with the firstfatty acid alkyl ester (from PKO) in a ratio of about 45-55 weightpercent to 55-45 weight percent, respectively. The resulting mixture isthen sulfonated in a falling film reactor and the resulting fatty acidalkyl ester sulfonic acid is reacted with NaOH to obtain a sodiumα-sulfofatty acid ester. This sodium α-sulfofatty acid ester is thenadded to other detergent components to obtain a final detergentcomposition.

EXAMPLE 3

A C₁₆-enriched methyl ester sulfonate is prepared according to thefollowing process. Palm kernel oil is combined with a C₁₆-enrichedfraction of fatty acids from tallow. The enriched mixture is thenesterified with an alkanol and then sulfonated in a falling filmreactor. The resulting fatty acid alkyl ester sulfonic acid is reactedwith NaOH to obtain a sodium α-sulfofatty acid ester.

Having described in detail the present invention, the invention definedby the appended claims is not limited by particular details set forth inthe above description, as many apparent variations thereof are possiblewithout departing from the spirit or scope thereof.

We claim:
 1. A composition, comprising a broad cut of C₁₀, C₁₂, C₁₄, C₁₆and C₁₈ α-sulfofatty acid esters comprising methyl ester sulfonatesderived from natural fats or oils and having an enriched C₁₆ or C₁₈α-sulfofatty acid ester concentration.
 2. The composition of claim 1,wherein the mixture is enriched for C₁₆ α-sulfofatty acid esters.
 3. Thecomposition of claim 2, wherein the C₁₆-enriched α-sulfofatty acid esterconcentration is at least about 25 weight percent C₁₆-enrichedα-sulfofatty acid ester of the total α-sulfofatty acid esters.
 4. Thecomposition of claim 2, wherein the C₁₆-enriched α-sulfofatty acid esterconcentration is at least about 35 weight percent C₁₆-enrichedα-sulfofatty acid ester of the total α-sulfofatty acid esters.
 5. Thecomposition of claim 2, wherein the C₁₆-enriched α-sulfofatty acid esterconcentration is at least about 50 weight percent C₁₆-enrichedα-sulfofatty acid ester of the total α-sulfofatty acid esters.
 6. Thecomposition of claim 1, wherein the enriched α-sulfofatty acid estersare C₁₆ methyl ester sulfonates.
 7. The composition of claim 1, whereinthe α-sulfofatty acid esters comprise a first and a second α-sulfofattyacid ester.
 8. The composition of claim 7, wherein the firstα-sulfofatty acid ester is prepared from palm kernel oil, cohune oil orcoconut oil, and the second α-sulfofatty acid ester is prepared frompalm stearine oil or tallow.
 9. The composition of claim 7, wherein thesecond α-sulfofatty acid ester comprises predominately C₁₆ chainlengths.
 10. The composition of claim 7, wherein the first α-sulfofattyacid ester comprises C₁₈, C₁₀, C₁₂, C₁₄, C₁₆, and C₈ chain lengths andthe second α-sulfofatty acid esters comprises predominately C₁₆ chainlengths.
 11. A detergent composition, comprising at least about 15weight percent of a mixture of C₁₂, C₁₄ and C₁₆ methyl ester sulfonatesand having a C₁₆-enriched α-sulfofatty acid ester concentration.
 12. Thedetergent composition of claim 11, wherein the mixture comprises first amethyl ester sulfonate comprising C₈, C₁₀, C₁₂, C₁₄, C₁₆, and C₁₈ chainlengths and a second methyl ester sulfonate comprising predominately C₁₆chain lengths.
 13. The detergent composition of claim 12, wherein thesecond methyl ester sulfonate consists of C₁₆ chain lengths.
 14. Thedetergent composition of claim 11, wherein the mixture consistsessentially of methyl ester sulfonates.
 15. A detergent composition,comprising at least about 35 weight percent of methyl ester sulfonatescomprising: a first methyl ester sulfonate comprising a mixture ofdifferent chain lengths; and a second methyl ester sulfonate comprisingat least about 35 weight C₁₆ chain lengths.
 16. A composition,comprising: about 60 to about 40 weight percent methyl ester sulfonatecomprising a mixture of chain lengths; and about 40 to about 60 weightpercent methyl ester sulfonate consisting essentially of C₁₆ chainlengths.
 17. A method for making a detergent composition, comprising:providing a mixture of α-sulfofatty acid esters with a C₁₆ enrichedconcentration; and combining the mixture of α-sulfofatty acid esterswith at least one other detergent component.
 18. The method of claim 17,wherein the α-sulfofatty acid esters comprise methyl ester sulfonates.19. The method of claim 18, including providing the mixture ofα-sulfofatty acid esters by providing a methyl ester feedstock and thensulfonating the methyl ester feed to make the methyl ester sulfonates.20. The method of claim 19, including sulfonating the methyl esterfeedstock by reacting the methyl ester feedstock with gaseous SO₃. 21.The method of claim 19, wherein the methyl ester is prepared from anatural fat or oil.
 22. The method of claim 19, further comprisingenriching the C₁₆ content of the methyl ester feedstock.
 23. The methodof claim 19, further comprising combining a natural fat or oil and anenriched natural fat or oil to form the methyl ester feedstock.
 24. Themethod of claim 23, including combining about 60 to about 40 weightpercent of the natural fat or oil with 40 to about 60 weight percent ofthe enriched natural fat or oil.
 25. A method for making a detergentcomposition, comprising: providing a methyl ester feedstock comprisingmethyl esters having a C₁₆ enriched concentration; sulfonating themethyl ester feedstock to obtain a C₁₆ enriched methyl ester sulfonate;and combining the methyl ester sulfonates with at least one otherdetergent component.
 26. The method of claim 25, the methyl estercomprising a first natural fat or oil comprising a mixture of chainlengths and a second natural fat or oil comprising predominately C₁₆chain lengths.
 27. The method of claim 25, further comprising enrichingthe C₁₆ content of the second natural fat or oil by removing at leastsome of the non-C₁₆ chain lengths.